Most Spoilers will have AXY pickups (see the Spoiler on my profile picture) The shell size of an AXY is roughly the same as that of a FatBoy, but the size of the magnet and coils in an AXY are the same as in an MXY (see the Epic in the same picture), it just has a bigger shell. The shell of a Fatboy is not oversized: it has a larger magnet and coils.

A fellow Club member let me try out a Fatboy, and I liked it in the bridge position - it definitely added beef to the tone, but it also lacked that high-end sparkle that you get with the narrow aperture of an AXY/MXY.

I traded out both AXY4's (I know it's a five-string, by I have the 'Classic' neck taper where the 4-string shell is appropriate) for FatBoys on the BigRedBass.

The 'Boys do sound more 'MusicMan-ish'. I describe the difference like this:

The AXY's sound like very, very good studio monitors: Letter-perfect representation, but that monitor-ish 'flat' EQ feel.

In comparison for me, the FatBoys sound more like high-end stereo speakers: A very good representation, but with some dips and peaks in the right place, more 'meat on the bones'. May be possibly just a bit louder, but a very small difference.

Although you can't go wrong with either one, I would not go back to AXY's, they were always just a bit pristine for me.

And why Alembic does NOT build a replacement Activator with a FatBoy in a MusicMan shell is beyond me. One of these in a StingRay with a proper Alembic harness would be extremely formidable, and I really like OEM MM pickups.

Thanks for your excellent comments on the Fatboy pickups. No one to this day has dexcribed it this way. Mica expressed that she feels the Fatboy pickup sounds more like a series pickup than the MXY/AXY. Pickup height, set up, electronics and playing style all have a say in how these things sound in the end....let's not forget body/neck woods!